Flex-to-Rigid (F2R): A Generic Platform for the Fabrication and Assembly of Flexible Sensors for Minimally Invasive Instruments

Abstract

The flex-to-rigid (F2R) platform allows for the fabrication of miniature and flexible sensor assemblies for minimally invasive medical instruments such as catheters and guidewires. Devices fabricated on silicon wafers are transferred onto polyimide and partially rendered flexible by means of a two-step backside silicon deep reactive ion etching. The flexibility allows for the devices to be folded into, or wrapped around the tip of the instruments. The fabrication of the whole assembly is based on standard integrated circuit manufacturing technologies so that it is possible to scale the devices down to the dimension of the smallest guidewires. Several demonstrations are presented to show the versatility of the F2R technology, and a polyimidebased flexible thermal flow sensor for application at the tip of a 360-µm diameter guidewire is introduced.

Ultra-Stretchable Interconnects for High-Density Stretchable Electronics

“…Here, the Flex-to-Rigid (F2R) microfabrication platform is adopted and extended to enable CMOS-type processing of highly stretchable (>1000%) interconnects with micron-scale interconnect footprints. F2R is a generic technology that makes CMOS devices flexible by etching the silicon ASICs into separate islands connected by flexible interconnects (formed from the original CMOS-produced interconnects of the ASICs) [ 20 , 21 ]. The strength of the F2R technology has been demonstrated by a flexible (not yet stretchable) ultrasound camera mounted on top of a catheter tip, which was microfabricated in a planar configuration ( Figure 1 d) and subsequently wrapped around a narrow tip ( Figure 1 c).…”

Pressure measurement of geometrically curved ultrasound transducer array for spatially specific stimulation of the vagus nerve

“…On the same wafer, 112 of these CMUT elements were aligned next to each other with 2 µm spacing. The Flex-to-rigid process [12], [13] was employed to use polyimide as a flexible layer that connects all elements, thus creating a flexible device which can curve.…”

Optical data link assembly for 360 µm diameter IVUS on guidewire imaging devices

“…Wirebonding or soldering these would not be a cost-effective solution. The Flex-2-Rigid (F2R) technology platform has been designed to overcome these issues [9].…”